Gemini Observatory's new imaging spectrograph,
without the help of adaptive optics, recently captured images that are
among the sharpest ever obtained of astronomical objects from the
ground.

Among the images and spectra acquired during
recent commissioning of the Gemini Multi-Object Spectrograph (GMOS) on
the 8-meter Gemini South Telescope, one image is particularly
compelling. This Gemini image reveals remarkable details, previously
only seen from space, of the Hickson Compact Group 87 (HCG87). HCG87 is
a diverse group of galaxies located about 400 million light years away
in the direction of the constellation Capricornus. A striking
comparison with the Hubble Space Telescope Heritage image of this
object, including resolution data, can be viewed at http://www.gemini.edu//index.php?option=content&task=view&id=104&Itemid=0&limit=1&limitstart=2.

"Historically,
the main advantage of large ground-based telescopes, like Gemini, is
their ability to collect significantly more light for spectroscopy than
is possible with a telescope in space," said Phil Puxley, Associate
Director of the Gemini South Telescope. He explains, "The Hubble Space
Telescope is able to do things that are impossible from the ground.
However, ground-based telescopes like Gemini, when conditions are
right, approach the quality of optical images now only possible from
space. One key area - spectroscopy of faint objects, which requires
large apertures and fine image quality - is where large telescopes like
Gemini provide a powerful, complementary capability to space-based
telescopes."

GMOS-South is currently undergoing
commissioning on the 8-meter Gemini South Telescope at Cerro Pachón,
Chile. "GMOS-South worked right out of the box, or rather, right out of
the 24 crates that brought the 2-ton instrument to Chile from Canada
and the UK - just like its northern counterpart did when it arrived on
Hawaii's Mauna Kea," says Dr. Bryan Miller, head of the commissioning
team. "The GMOS program demonstrates the advantage of building two
nearly identical instruments. Experience and software from GMOS-North
have helped us commission this instrument more rapidly and smoothly
than we could have done otherwise," explains Dr. Miller. He adds,
"Although the images from GMOS-South are spectacular, the instrument is
primarily a spectrograph and that is where its capabilities are most
significant for scientists." GMOS-South is expected to begin taking
science data in August 2003.

As a multi-object
spectrograph, GMOS is capable of obtaining hundreds of spectra in one
"snapshot." The ability to deliver high-resolution images is a
secondary function. "It used to take an entire night to obtain one
spectrum," explains Dr. Inger Jørgensen, who led the commissioning of
the first GMOS instrument on the Frederick C. Gillett Gemini Telescope
(Gemini North) over a year ago. "With GMOS, we can collect 50-100
spectra simultaneously. Combined with Gemini's 8-meter mirror, we are
now able to efficiently study galaxies and galaxy clusters at vast
distances - distances so large that the light has traveled for half the
age of the Universe or more before reaching Earth. This capability
presents unprecedented possibilities for investigating how galaxies
formed and evolved in the early Universe."

GMOS
achieves this remarkable sensitivity partly because of its
technologically advanced detector, which consists of over 28 million
pixels, and partly because of multiple innovative features of the
Gemini dome and telescope that reduce local atmospheric distortions
around the telescope. "When we designed Gemini, we paid careful
attention to controlling heat sources and providing excellent
ventilation," said Larry Stepp, former Gemini Optics Manager. Stepp
elaborates, "For example, we constructed 3-story-high vents on the
sides of the Gemini enclosures. It is great to see this image that
provides such a dramatic validation of our approach."

"The
twin Gemini Telescopes offer a unique advantage," explains Director of
the Gemini Observatory Dr. Matt Mountain. "Now that both telescopes are
equipped with nearly identical GMOS instruments, we have created an
unprecedented uniform platform to coherently study and take deep
spectra of any object in the northern or southern sky at optical
wavelengths."

Upgrades to GMOS-South that will
increase its variety of capabilities are planned even as the instrument
is undergoing commissioning. An Integral Field Unit (IFU) on GMOS-South
is anticipated to begin commissioning in early 2004. Jeremy
Allington-Smith, leader of the IFU team at the University of Durham
said, "GMOS-South will soon be fitted with an integral field unit like
its sister on Gemini North. Made by the University of Durham, it uses
more than a thousand optical fibers, tipped at each end with
microscopic lenses, to dissect the object under study. This gives GMOS
a 3-D view of the target, in which each pixel in the image is replaced
by a spectrum. This innovation allows GMOS to make detailed maps of,
for example, the motion of stars and gas in galaxies."

GMOS
was built as a joint partnership between Gemini, Canada and the UK.
Separately, the U.S. National Optical Astronomy Observatory provided
the highly capable detector subsystem and related software (http://www.noao.edu/usgp).
It is anticipated that GMOS-South will be available for full scientific
operations in August 2003 when astronomers from the seven-country
Gemini partnership will begin using the instrument for a wide variety
of scientific studies.

During
commissioning in early 2003 of the Gemini Multi-Object Spectrograph
(GMOS) on the Gemini South Telescope, images and spectra were obtained
of the group of galaxies known as the Hickson Compact Group 87 (HCG
87). The Gemini image (shown, left) compares very favorably with the
Hubble Space Telescope Heritage image of this same field and
illustrates the remarkable resolution that is possible with Gemini when
atmospheric conditions are optimal.

The
three Gemini images used to make the color composite image have
resolutions between 0.36 and 0.5 arcseconds (full-width-half-max) and
an unsharp mask has been applied to highlight details in the major
galaxies. Technical details on the images can be found here.

About Hickson Compact Group 87:

One
of the primary galaxies of the HCG87 group is an edge-on galaxy with
dust lanes, which is a beautiful example of a box/peanut shaped central
bulge that the eye perceives as an X-shaped structure. This morphology
is due to the vertical instability of the orbits of millions of stars
going around the center of the galaxy. This can be caused by
interactions with other galaxies, including the accretion of dwarf
galaxy companions, or by the presence of a bar-shaped structure. Thin
bars are unstable structures that buckle about their midpoints out of
the plane of the bar. The warp in the disk of the galaxy and the lack
of a clear bar signature in the galaxy's spectrum suggest that the
X-structure in this galaxy is due to an interaction. The image also
includes other galaxies including a more face-on spiral and an
elliptical. All of these galaxies move through space together and
perform a slow graceful gravitational dance as they evolve and
influence each other's structure.

A
longslit spectrum of HCG87a (box/peanut galaxy). The slit was placed
along the major axis (long dimension) of the galaxy and the light was
dispersed with a 400 line/mm diffraction grating to detect three
emission lines from gas in the galaxy. Halpha is the brightest line
emitted by Hydrogen gas at 6563A. The [NII] lines are emitted by
ionized nitrogen gas. Doppler shift due to movement of the gas causes
the observed wavelengths of the lines to shift with position along the
slit. The gas to the rights of the galaxy's center is moving away from
us at 350 km/sec with respect to the center of the galaxy while gas to
the left is moving towards us. This shows that the galaxy is rotating.
The bright vertical spectrum along the right edge is from a nearby
star. The horizontal lines along the top of the image are emission
lines from gas in the earth's atmosphere.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai'i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.